Internal combustion engines combust a mixture of fuel and air in order to produce torque to propel a vehicle. Specifically, air is drawn into the engine via an engine intake manifold based on a position of a throttle, and then the air is mixed with fuel. The air-fuel mixture is combusted within engine cylinder(s), to drive piston(s) within the cylinder(s), thus rotating an engine crankshaft. By-products of combustion within the engine cylinders are routed to one or more catalysts via an exhaust manifold, prior to exiting to atmosphere.
Both the engine intake and exhaust systems may exhibit degradation, over time. Any presence of degradation in the intake system, exhaust system, or engine may lead to a decrease in fuel economy, and in some examples may lead to an increase in undesired emissions. The inventors have herein recognized these issues.
Engine operation may be regulated based on a number of parameters, such as the air flow rate provided to the engine. A measurement of air flow provided to the engine may be determined by a mass air flow (MAF) sensor, for example. However, in the intake manifold, any presence of degradation downstream of the MAF sensor may result in unmetered air being provided to the engine. As a result, the air-fuel ratio may switch lean. However, there are many other root causes for an engine running lean, such as undesired combustion, exhaust gas oxygen sensors that are not functioning as desired, valve timing issues, the MAF sensor not functioning as desired, etc. Thus, it can be challenging to specifically diagnose the presence or absence of degradation stemming from an intake system or intake manifold downstream of a MAF sensor. Similarly, degradation in the exhaust system may be difficult to pinpoint, if said degradation is downstream of an exhaust gas oxygen sensor, for example.
U.S. Patent No. US20090187301 teaches a method of diagnosing the presence or absence of degradation in an intake manifold of an engine, by comparing manifold absolute pressure to atmospheric pressure. In one example, a significant amount of degradation is indicated responsive to manifold absolute pressure being substantially equivalent to atmospheric pressure.
However, the inventors herein have recognized potential issues with such a method. For example, such a method is unable to diagnose the presence or absence of degradation in an exhaust system of the vehicle. Thus, the inventors have herein developed systems and methods to address such issues. In one example, a method is provided, comprising conducting an engine system diagnostic by rotating an engine of a vehicle unfueled to draw an intake air flow into the engine via an intake manifold and to route an exhaust flow via an exhaust system to atmosphere, and indicating a source of degradation stemming from one of the engine, the intake manifold, or the exhaust system based on both the intake air flow and the exhaust flow during the rotating. In this way, a robust determination of whether a source of degradation stems from either the intake manifold, the engine, or the exhaust system of the vehicle with one engine system diagnostic.
In one example, the method includes prior to conducting the diagnostic, obtaining a set of baseline comparator data that includes a baseline air intake flow and a baseline exhaust flow under a substantially equivalent set of conditions as that for conducting the engine system diagnostic, including rotating the engine unfueled via a motor powered by a battery. In such an example, the substantially equivalent set of conditions further comprises rotating the engine at a predetermined speed for a predetermined duration of time, and controlling a throttle positioned in the intake manifold to a predetermined position to allow air to be drawn into the engine via the intake manifold.
In some examples, the intake air flow and the baseline intake air flow may be measured via a mass air flow sensor positioned in the intake manifold, and where the exhaust flow and the baseline exhaust flow is measured via a pressure sensor positioned in the exhaust system. In such an example, the pressure sensor may comprise a differential pressure sensor corresponding to a gas particulate filter positioned in the exhaust system. Furthermore, obtaining the set of baseline comparator data may be conducted under conditions where the engine system is free from the source of degradation.
In one example, the source of degradation may be indicated in the intake manifold responsive to the intake air flow during the engine system diagnostic being substantially equivalent to the baseline intake flow, but where the exhaust flow during the engine system diagnostic is greater than the baseline exhaust flow.
In another example, the source of degradation may be indicated in the exhaust system responsive to the intake air flow during the engine system diagnostic being substantially equivalent to the baseline intake air flow, but wherein the exhaust flow is lower during the engine system diagnostic as compared to the baseline exhaust flow.
In another example, the source of degradation may be indicated as stemming from the engine responsive to both the intake air flow and the exhaust flow during the engine system diagnostic being lower than the baseline intake air being lower than the baseline intake air flow and the baseline exhaust flow, respectively.
In still another example, the source of degradation may not be present in any of the intake manifold, exhaust system, or engine responsive to both the intake air flow during the engine system diagnostic being substantially equivalent to the baseline intake air flow, and the exhaust flow during the engine system diagnostic being substantially equivalent to the baseline exhaust flow.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.